Claude Code MCP Traffic Hijacked to Steal OAuth Tokens

A new man-in-the-middle (MitM) attack has been identified, targeting Anthropic's Claude Code ecosystem. Threat actors exploit vulnerabilities in the Model Context Protocol (MCP) traffic to intercept OAuth authentication tokens. This attack allows unauthorized access to enterprise SaaS platforms such as Jira, Confluence, and GitHub. Researchers from Mitiga Labs have detailed a five-step attack chain that redirects MCP traffic through attacker-controlled infrastructure. The attack leverages weak protections in the local Claude Code configuration file, specifically ~/.claude.json. As of now, no patch has been released by Anthropic to mitigate this vulnerability. Organizations using Claude Code are at risk of unauthorized access and data breaches. The attack is significant due to the potential for broad access to sensitive enterprise data.

Key Points: • Hackers exploit Claude Code MCP traffic to hijack OAuth tokens. • The attack allows unauthorized access to major SaaS platforms like Jira and GitHub. • No patch has been released by Anthropic to address this vulnerability.